1. Field of the Invention
The present invention relates to agents which have an anti-apoptotic effect on cells involved in wound healing. In particular, the present invention relates to the use of substances which bind either to IAP and/or to integrin αvβ3 and/or to thrombospondin 1 in such a way that the binding between thrombospondin 1 and IAP and/or integrin αvβ3 is inhibited, thus reducing the rate of apoptosis of cells associated with wound healing, for producing medicaments which are suitable for the treatment of traumatic conditions, preferably chronic wounds. Preferred exemplary embodiments encompass the amino acid sequences depicted in SEQ ID Nos 1-11, and peptidomimetics derived therefrom. The present invention further relates to cells having a significantly reduced rate of apoptosis, it being possible to use these cells preferably as constituent of a so-called artificial skin which has already been described in the prior art, and the skin being mechanically tensioned before application of this skin to the wound, and the corresponding cells preferably being treated additionally with the agents of the invention.
2. Description of Related Technology
The process of wound healing consists of three phases during which the injured tissue is repaired and is thus regenerated, after which the new tissue becomes manifest as scar.
These three phases are classified in the following way:    (a) inflammatory phase which starts after 0 to 3 days    (b) a subsequent cellular proliferation phase of 3 to 12 days, and    (c) a restorative phase of 3 days to about 6 months.
In the inflammatory phase, inflammatory cells, mainly neutrophils, collect at the wound site, followed by lymphocytes, monocytes and even later macrophages.
During the proliferation phase, the so-called granulation tissue (highly vascularized connective tissue which forms during the healing of wounds, ulcers inter alia) is formed in the injured area. An important part is played in this by, in particular, fibroblasts and epithelial cells (re-epithelization), besides other cell types. The fibroblasts produce the collagen which is important for wound healing.
Ascorbic acid (vitamin C) is essential for the formation of collagen. It has already been shown in several investigations that the use of ascorbic acid activates the reduced proliferative activity and the collagen synthetic activity of aged skin fibroblasts, and therefore wound healing is improved. However, the mode of action has not been shown, but inter alia an involvement of vitamin C in lipid oxidation processes is described.
During the re-epithelization, the epithelial cells proliferate and migrate from the edges of the wound into the tissue. It has been possible to show in this connection that re-epithelization can be promoted by wound dressings which represent a moisture barrier.
The concluding phase of wound healing is characterized by the replacement of the granulation tissue by collagen and elastin fibers and the devascularization of the granulation tissue (i.e. formation of scar tissue). Recent studies have moreover shown that topical application of antioxidants such as alpha-tocopherol reduces scar formation and normalizes blood coagulation during therapy.
Fibroblasts and epithelial cells in particular therefore play an important part in wound healing. The low proliferation activity of the fibroblasts and the small number thereof impedes favorable wound healing. In many cases there is use, besides antiinflammatory substances, also of substances such as growth factors which are intended to enhance the proliferation abilities or the synthetic activity of the cells involved.
Apoptosis (synonym: programmed cell death) is an irreversible process. An apoptotic cell inevitably dies. Apoptotic fibroblasts have been suggested to have a negative role in wound healing, but no way has yet been proposed for having a beneficial influence on the rate of apoptosis of fibroblasts during wound healing by bringing particular medicaments, i.e. molecular remedies, into contact with the fibroblasts.
European patent application EP-A-0 903 149 describes a method for identifying apoptosis-inducing substances in immune cells. It was shown that substances which bind to the integrin-associated protein (IAP or CD 47) on the surface of immune cells may have the ability to induce apoptosis. The mechanisms of action were not described.
It has already been proposed that IAP is involved in the formation of a specific calcium channel (Schwartz, M. A. et al., Journal of Biological Chemistry, 268:27, 19931-19934). No mention was made of a role of this hypothetical calcium channel in the induction of apoptosis.
The applicant's international patent application WO 01/33218 A1 of earlier priority, the full contents of which are incorporated in the present application by reference, describes a method for identifying apoptosis-inhibiting substances and the use of such substances for producing medicaments for the treatment of vascular disorders and as active principle in a pharmaceutical preparation for the treatment of vascular disorders. A use of such substances for producing medicaments for promoting wound healing or as active principle of a pharmaceutical preparation for the treatment of wounds was not described.
One of the most modern approaches to the treatment of chronic wounds is the use of a so-called living skin as skin substitute or wound-covering means. There has already been a large number of patent applications in this area. Mention may be made here representatively to EP 1 005 873 of Isotis N.V. or the international patent application WO 99/43787 of Advanced Tissue Sciences Inc. The principle of the production of such an artificial skin is to grow either autologous or heterologous cells (skin cells) on a biocompatible membrane and then use this artificial skin as remedy. However, it has not previously been described that it is beneficial or necessary to inhibit the apoptosis of the cells used in order to ensure a more favorable progress of the healing. Neither stretching of the artificial skin nor the addition of anti-apoptotic agents is proposed. A negative effect of apoptosis on the progress of healing is not discussed in these patent applications and is not made obvious to the skilled worker.
A healing influence of chronic traumatic conditions or large-area and/or deep wounds, like those frequently occurring in burn injuries, in particular is possible at present, despite the prior art mentioned, only with difficulty.
There is thus still a great need in the art for improved means which beneficially influence wound healing, and in particular also the healing of chronic wounds or large-area wounds or burn injuries of the skin.